Reduction of tolylene diamines



United States Patent 3,445,516 REDUCTION OF TOLYLENE DIAMINES James M. Cross, New Martinsville, W. Va., assignor to Mobay Chemical Company, Pittsburgh, Pa., in corporation of Delaware No Drawing. Filed Jan. 28, 1966, Ser. No. 523,569 Int. Cl. C07c 85/14 US. .Cl. 260563 10 Claims ABSTRACT OF THE DISCLOSURE Hydrogenation of tolylene diamines is improved by charging a tolylene diamine and a member selected from the group consisting of low boilers obtained in the hydrogenation of tolylene diamine and residue obtained in the hydrogenation of tolylene diamine.

The foregoing objects and others which will become apparent from the following description are accomplished in accordance with the invention, generally speaking, by providing a method of hydrogenating tolylene diamine wherein either the low boiler, the residue or both obtained in the hydrogenation of tolylene diamine is charged together with the tolylene diamine for the hydrogenation. That is, in addition to tolylene diamine, either low boiler, residue or both can be used. By utilizing such mixtures, the yields of hydrogenated tolylene diamine obtained are greatly improved.

The following theory is believed to be the mechanism by which the yields are improved, however, this theory is not presented herein for the purpose of limitation and should not be construed to bind the applicant. In the hydrogenation of tolylene diamine, several reactions occur and by-products are formed in addition to the reduced tolylene diamine. These reactions are set forth by the following equations:

catalyst NH2 3H; NH2

1 NH: NHE

Hydrogenation II. CH3

catalyst 2 NH2 NH: NH:

Autoalkylation III. CH CH3 catalyst S -NH2 H2 NHz l NHz Hydrogenolysis NH;

3,445,516 Patented May 20, 1969 In Equation I above, tolylene diamine, which is represented throughout the equations as the 2,4-tolylene diamine isomer, is hydrogenated in the presence of a suitable catalyst to yield hexahydrotolylene diamine. It should be understood that throughout the equation, isomers of tolylene diamine other than the one set forth above, can also be hydrogenated and enter into the same reaction set forth, but, for the purpose of simplicity, the 2,4-isomer is shown. It is also possible, though less probable, for the autoalkylation reaction to occur by reaction of amine groups other than the p-amino groups. In Equation II, two mols of 2,4-hexahydrotolylene diamine undergo autoalkylation to yield a secondary amine plus ammonia. In the Equation III, hexahydrotolylene diamine reacts further with hydrogen in the presence of a catalyst to yield by hydrogenolysis a cycloaliphatic monoamine plus ammonia. Since either of the amino groups of the 2,4-hexahydrotolylene diamine can enter into the hydrogenolysis reactions the product is shown without indicating the position of the amino group. In both Equations II and III, ammonia is formed in addition to the organic compound shown. The presence of ammonia is also believed to be detrimental to the catalyst which is required for the hydrogenation to occur. After the reaction is completed, the product is distilled. After removal of the ammonia and small amounts of water, a mixture consisting essentially of cycloaliphatic monoamines plus other trace impurities is distilled over first. This fraction is hereinafter referred to as low boiler. Next the main fraction, which is reduced tolylene diamine, is distilled over. Then a last or final fraction, which is mainly tolylene diamines, but contains traces of unknown impurities such as the secondary amine shown in Equation II, distills over. This last fraction is hereinafter referred to as residue. By practicing the process in accordance with this invention, by including either the low boiler or the residue (tolylene diamine plus impurities) in the reaction along with the aromatic diamine, the Equations II and III are driven to the left thereby diminishing the formation of the ammonia and increasing the yield of the desire-d reduced diamine.

In the practice of this invention, any suitable hydrogenation catalyst may be used, such as, for example, nickel kieselguhr, Raney nickel, Raney cobalt, cobalt oxide, a cobalt oxide-calcium oxide mixture, ruthenium, palladium, platinum, rhodium, a mixture of cobalt oxidecalcium oxide in sodium carbonate, ruthenium dioxide, sodium ruthenate on carbon, platinum oxide and the like. It is preferred that the mixture of cobalt oxide-calcium oxide and sodium carbonate be used.

' In the preparation of hexahydrotolylene diamine, any isomer or isomeric mixture of tolylene diamines can be used as the starting material. Commercially available isomeric mixtures are 80% 2,4- and 20% 2,6-tolylene diamines containing small quantities of other isomers and 2,4-tolylene diamine and 35% 2,6-tolylene diamine containing small quantities of other isomers. These isomeric mixtures, in addition to substantially pure isomers, which have been separated from isomeric mixtures, generally contain small quantities of o-diamines such as, for example, 2,3- or 3,4-tolylene diamines. The invention described herein is suitable for the hydrogenation of all isomericmixtures of tolylene diamine including those containing o-diamines.

In accordance with this invention, any quantity of low boiler or residue or both that is included along with the aromatic diamines will improve the yield obtained. Howere, it is preferred to include from about 10 to about 20% of this low boiler based on the quantity of tolylene diamine used and from about 3 to about 30% and for best results, from about 5 to 15% of the residue based on the quantity of tolylene diamine used.

In order to conduct the hydrogenation, suitable tem peratures and pressures should be used. These reaction conditions are generally known and are not the basis of patentability of this invention. However, it is preferred that temperatures of at least 200 C. be used. Desirably, from about 200 to 300 C. should be used with temperatures within the range of from about 230 to 270 C. giving the best results. Any suitable pressure can be used,

4 previous reduction are charged together with the ingredients stated. About 137 parts of reduced tolylene diamine are obtained. This represents a yield of about 84%.

EXAMPLE 3C The procedure of Example 3A is repeated, however, about 20 parts of low boiler are added in addition to the ingredients stated. About 127 parts of reduced tolylene are obtained. This represents a yield of about 78%.

however, it is preferred that pressures within the range EXAMPLE 3D of 500 to 4000 p.s.i. be used.

The invention is further illustrated but not limited by The procedure of Example 3A is repeated, however, the following examples in which parts are by weight unabout 20 parts of low boiler and 20 parts of residue are less otherwise specified. added in addition to the ingredients stated. About 153.5

EXAMPLE parts of reduced tolylene diamine are obtained. This represents a yield of about 94%. General Procedure Although the invention has been described in con- The quantity of tolylene diamine indicated the followslderable detal! h the foregomg, it Is to be hhdersthod ing table either free f of containing o diamine as that such detail is solely for the purpose of illustration dicated, together with the quantity of residue and/or low f that h Vananohs be made Y fhose Sklhed boiler indicated in the table, are charged to a one-liter m f departlhg from the splrlt and P stainless steel autoclave and 30 parts of cobalt oxide, 45 0f the Invention. parts of calcium oxide and 19.5 parts of sodium carbon- What 13 clalmed 153 ate as catalyst are added. The autoclave is closed, purged In the method reduclhg y h fhamlne t0 with hydrogen gas to remove all oxygen present, heated hexahydfotolylene dltlmlne y hydrogenatmg 111 the P to about 180 C. and stirred. The temperature is raised ence a hydrogenation Catalyst, f )mprovemem Whlch to that indicated in the table and the autoclave is pres- COITIPFISCS Charging a tolylene. {hamlfle and membfir surized with hydrogen to the pressure set forth. The reh h Q the up cql'lslstlng of holler P- action is continued for 2 to 3 hours, as indicated, at which P 15mg i y cycloahphflflc 'mOIIORmIYIFS obtalnefi In time, the absorption of hydrogen has practically stopped. hyrogenatlon 0f t yl d1am 1ne aIld Tesldue comprlsfhg The autoclave is cooled to approximately 80 to 120 C. malnly tolylfme'dlamlnes Ohtalned the hydrogenatlon and the material discharged therefrom. The catalyst is of tolylene dlamlneremoved from the amine and the centrifuge cake is washed 2. The process of claim 1 wherein the group member with small amounts of methyl alcohol to remove the last is l w iler. amine from the catalyst. The methanol extract is com- 3. The process of claim 1 wherein the group member bined with the filtrate and fractionally distilled. is residue.

TABLE Parts by weight Reaction 1 Distillate Tolylene Tempertime in Parts of parts of Parts of Yield, Example No. Low boiler diamine Residue ature, C. hours low boiler TDA residue percent None 3 300 None 230 3 67. 5 214. 3 1s 72. 5 None 3 300 40 230 3 17. 1 300 19. 2 s9 30 a 300 None 230 3 247 13. 5 s2. 2 60 3 286. 5 13. 5 230 3 71. 5 271 13. 2 92 None 300 None 230 3 49 229. 5 13 76 10 4 300 13 230 3 59 249 26. 5 s3 40 5 300 13 230 2 66. 2 259.2 15. 3 s3 1 The rate of hydrogenation is observed by pressuring the autoclave to 4,000 p.s.i. and permitting the pressure to drop to 3,500 p.s.i. then pressuring back to 4,000 p.s.i. and this is repeated until the period of time indicated lapses.

2 Control, no low boiler or residue added.

It was observed on repeated runs using catalysts from the previous run that the yield diminished with each reuse of the catalyst, indicating that some poisoning effect on the catalyst has occurred.

EXAMPLE 3A (COMPARISON) About 156 parts of 2,4-tolylene diamine substantially free of o-diamine isomers in about 600 parts by volume of dioxane as solvent, and about 5 grams of ruthenium dioxide are charged to a one-liter stainless steel autoclave. The autoclave is purged with hydrogen gas to remove all oxygen, heated to about 180 C. and stirred. The temperature is raised to about 144 C. at a pressure of about 4000 p.s.i for about 4% hours at which time the absorption of hydrogen has substantially stopped. The autoclave is cooled and the contents distilled to remove solvent. The low boiler is removed with the solvent. The product contains about 115.2 parts of reduced tolylene diamine. This represents a yield of EXAMPLE 3B The procedure of Example 3A is repeated with the exc ption that about 2.0 parts of residue obt ined in a 3 Pure 2,4-t01ylene diamine free of other isomers.

4 An isomeric mixture of 2,4- and 20% 2,6-to1y1ene diamine containing approximately 3% o-diamine.

5 An isomeric mixture of 80% 2,4- and 20% 2,6-tolylene diamine free of o-diann'ne.

4. The process of claim 1 wherein both low boiler and residue are charged.

5. The process of claim 1 wherein the tolylene diamine is substantially free of ortho-diamine isomers.

6. The process of claim 1 wherein the low boiler is present in an amount of from about 10 to about 20% by weight based on the tolylene diamine charged.

7. The process of claim 1 wherein the residue is present in an amount of from about 3 to about 50% by weight based on the tolylene diamine charged.

8. The process of claim 1 wherein the hydrogenation is conducted at a temperature of at least 200 C.

9. The process of claim 1 wherein the catalyst is a cobalt oxide catalyst.

10. The process of claim 1 wherein the hydrogenation is conducted at a pressure of at least 500 p.s.i.

References Cited UNITED STATES PATENTS 3,351,650 11/1967 Cross et al 260453 CHARLES B. PARKER, Primary Examiner,

P. C. IVES, Assistant Examiner. 

